Problems with VHF

[Dyak]

Evening Chaps,
I was out today and had problems with my fixed DSC VHF in that it would not transmit but received perfectly and appeared to be Ok in DSC mode.
Any clues what the problem might be? Bye the way its an Icom something or other. Can't remember the model number but it's 4 years old.

 

[William_H]

Presumably it has the push to talk button on the microphone. If you press the button and nothing happens ie you are still receiving (open the squelch to confirm) then the problem lies in the microphone button circuit cord or plug and possibly in the radio changeover circuit.
However if it does react but you can not call anyone then get a hand held or another boat very close to confirm no transmit (at all).
If it does transmit but just very close range then chances are you have an antenna problem. olewill

 

[Birdseye]

In order of likelyhood:
1/ aerial problem giving greater swr - what happens here is that the weak signal you receive can get down the aerial and you receiver is very sensitive whilst the 25w you try to transmit gets bounced back by the high impedance of the faulty aerial and the tranmit function switches off to protect the radio. check plug at back of radio, and try an alternative aerial
2/ low voltage at the radio resulting from a high resisitance supply. the power draw on tranmit drops the voltage too low to transmit.
3/ faulty press button on the radio.

aerial problem is way the most likely. internnal radio problem is way the least likely.

 

[st599]

Doesn't necessarilly need to be a high impedance problem to up the VSWR. Could be a short or near short.

 

[whipper_snapper]

[ QUOTE ]
it would not transmit but received perfectly

[/ QUOTE ]

What does that mean ? Did it appear normal but no-one replied ?! Did the transmit light come on when the PTT was pressed ?

what does appeared to be Ok in DSC mode mean? You mean it was transmitting DSC data ? If so under what circumstances?

Hard to diagnose without some more information.

 

[Ruffles]

I had the same problem caused by a disconnected braid on the cable connection. Fine on RX. Nothing TXd even listening on deck with a handheld. Assume you get a TX light when you press the button?

Apparently it's difficult to check with a continuity tester because some aerials appear open circuit.